The best explanation for why the concept of the global system of agriculture is helpful to geographers is:
Option D: The concept helps geographers simplify and visualize a vast and complicated global supply chain.
This option highlights the importance of understanding global agricultural processes in a broader context, allowing geographers to analyze and interpret the interconnections within the agricultural system, including the relationships between local practices and global markets, trade policies, and environmental impacts. The other options, while valid in certain contexts, do not encapsulate the overarching utility of the global agriculture system as effectively as Option D.